Formation of light-sensitive layers on photographic films



J y 1960 H. MANSFELD 2,945,771

FORMATION OF LIGHT-SENSITIVE LAYERS on PHOTOGRAFHIC FILMS Filed y 3. 1955 INVENfiZ? HusERT llA/VJFHD Hubert Mansfeld, Eduard-Steiule-Str. 7, Stuttgart-Sillenbuch, Germany Filed May '3, 19'55, Ser. No. 505,722

7 Claims. (Cl. 117-34) This invention relates to processes for depositing lightsensitive films on suitable bases therefor, especially for purposes of photography.

It is an object of the present invention to provide means facilitating formation of light-sensitive layers on strip-like carriers adapted to be used as photographic films, photosensitive registering strips, and like indexing or image-receiving means, whereby highly eificacious sensitized films may be produced independently of the physical characteristics of the material of which the carrier is constituted.

It is another object of the present invention to provide means contributing to efficient and simplified production of photographic films and like optically sensitive elements by sublimation, under vacuum, of light-sensitive substances onto respective surfaces of suitable bases or can riers in such a manner that blurring of the films is prevented.

It is still another object of the present invention to provide means conducive to uniform and accurate formation of photographic film strips and like image receiving structures employing layers of optically responsive materials deposited by vapor condensation under predetermined conditions of temperature and vacuum on hands, strips, or sheets of appropriate base materials, said conditions and the relation of said bands to a source of said vapors being so chosen that the possibility of defective formation of said layers is substantially eliminated;

Still another object of the invention is to provide means ensuring production of optically responsive films" and strips for photographic purposes in an economic and technically advantageous manner, whereby the cost of production is materially reduced while the rate of production is enhanced without loss of quality of the finished product.

I-Ieretofore known processes for applying light-sensitive layers to fiat bases, such as strips or sheets, for photographic purposes involved depositing such layers in the form of emulsions on said bases or impregnating a base such as paper with a solution or emulsion of the light-sensitive substances.

It has already been proposedto deposit light-sensitive layers on carriers or bases therefor by condensing the component substances onto the bases from their vapor or gaseous phases. In order to practice such a process, it was contemplated that a stationary glass plate and a glowing body, provided with the substance to be deposited on said plate, be jointly disposed in a suitable glass vessel. Subsequentto evacuation of the vessel and heating of the glowing body by means of an electric current, the lightsensitive substance was to be Sublimated onto the surface of the glass plate.

However, this process never came into general use or attained any substantial degree of practical importance because it was much too diificult and expensive to carry out. The surface area of the base to be covered by the sensitive layer was limited by the dimensions "of the 2,945,711- Patented July 19', 1960 evacuated vessel or receptacle. Moreover, after each vaporization was terminated, the vessel had to be opened for the removal of the coated base, which, of course, necessitated a reevacuation of the vessel prior to the next vaporization process.

A further disadvantage of the above-mentioned pro posed process resided in the fact that the base or carrier was stationarily exposed both to the heated vapors and to the radiation emanating from the vapor source, so that the temperature of the base would often rise very high. As a result, only non-inflammable and highly heatresistant materials could be employed as the base or carrier, quite apart from the fact that condensation of the vapors in suflicient quantities can be obtained only when the carrier surface is at a temperature considerably lower than the vapors themselves.

It is therefore, another primary object of the present invention to provide a process which, in conjunction with greater economy in operation, eliminates the above set forth disadvantages and makes it possible to deposit all types of light-sensitive substances, such as the silver halides, onto continuously and unidirectionally running bands or strips, such as cellulose films, paper, and the like, independently of the thermal characteristics of the film base material. The base or carrier to be coated is preferably a band or strip disposed in roll form and is received in the vessel to be evacuated together with an empty spool and the source of the vapors.

These and other objects of the invention will become further apparent from the following detailed description, reference being made to the accompanying drawing, showing preferred embodiments of the invention.

In the drawing:

Fig. l is a sectional view of a photographic film strip, the view being taken along a line substantially perpendicular to the plane of said strip according to the invention;

Fig. 2 is a schematic illustration of one embodiment of the present invention;

Fig. 3 is a schematic illustration of another embodiment of the invention;

Fig. 4 is a schematic illustration of still another embodiment of the invention; and

Fig. 5 is a schematic illustration of yet a further em: bodiment of the present invention.

Referring now more particularly to Figs. 1 and 2, the vapor source consists of a crucible 13 in which the substance 14 to be vaporized is located. Upon heating of the crucible, as by electric heating means :15, the vapors emerge from the crucible through a suitable guide or discharge opening 16 disposed in the top of said crucible thus forming a source of vapors or a vapor generating means.

The carrier 11, which is to be coated with a photosensitive layer 12 to form a photographic film it is originally retained on an uncoiling feed or supply roll 17 and is continuously guided past opening 16 and in the immediate vicinity'thereof and thereafter over a pair of idler rollers 19 to a take-up or coiling roll 18 driven at any suitable speed by conventional means (not shown). The entire arrangement is located in an evacuated housing or vaporizing chamber 20.

By virtue of the fact that the film carrier is merely guided past the discharge opening of the heated crucible, its temperature rises only negligibly so that the vapors condense, directly after passing through the discharge opening, on a surface having a temperature considerably lower than the vaporization temperature. In this manner, light-sensitive layers of a thickness lying in the range of thicknesses having practical importance in photography may be produced. The layer thickness is, inter alia, dependent on the rate of movement of the carrier and of its surface structure, as well as on the emissivity of the vapor source, the crucible temperature, and the size of the crucible opening.

As will be readily understood, a relatively greater rate of movement imparted to the carrier requires a correspondingly greater emission of vapors per unit of time than a relatively smaller rate of movement. Greater quantities of vapors, of course, require higher crucible temperatures, but in no eventuality may the latter be raised so high that the substance being vaporized disintegrates or decomposes or that light radiation from the crucible walls illuminates the carrier and causes a darkening or blurring of the film.

Accordingly, the vaporization and condensation of the vapor is effected in a vacuum where the temperatures may be so regulated or controlled that on the one hand a sufficient emission of vapors is brought about while on the other hand decomposition or blurring of the film through light radiation is prevented. Depending on the intended use to which the completed and coated carrier is to be put, the vaporization temperature, and thereby the quantity of vapors emitted, can be increased or decreased.

Thus, for example, if the sensitized carrier strip is to be used for picture taking purposes, the crucible temperature must be considerably lower than it would have to be during coating of a carrier to be used only as a registering strip in devices or apparatuses employing an optical indicator. In the case of such a registering strip, blurring of the background is of relatively minor importance.

Due to a further refinement of the invention, however, it becomes possible to use substances during the vaporization which, if they were originally compounded, would disintegrate or decompose even though they would not be subject to blurring. This results from the fact that the individual components of the light-sensitive substance are separately contained and vaporized from respective crucibles, so that combination of said components into compound form takes place only at the instant of or immediately after the sublimation or condensation of the vapor phase.

A system for effecting formation of a light-responsive layer on a carrier or base by vaporizing the individual components or fractions of the optically sensitive compound of which such layer is constituted in schematically shown in Fig. 3. As before, the carrier 11 is fed from feed roll 17 past idler or guide rollers 19 to take up roll or spool 18, all of these being disposed in evacuated housing or vaporizing chamber 20.

Two crucibles 13 and 13" are provided within chamber 20 adjacent the path of movement of carrier 11. Crucible 13 is heated by suitable electric resistance or inductance heating means 15 and contains one element or substance 14', e.g., silver, of the photosensitive compound, e.g., silver bromide, to be formed. Crucible 13" is heated by electric heating means 15" and contains the other element 14", i.e., bromine, of the compound to be formed. As will be readily understood, elements 14' and 14 may combine while still in their gaseous phases immediately after leaving cricibles 13' and 13" through discharge openings 16' and 16", respectively, or they may first condense directly on the surface of carrier 11 and combine subsequent to such condensation, depending on the operating conditions existing in chamber or housing 20.

At the instant when the sublimation takes place, of course, the temperature is necessarily fairly low relative to the original vaporization temperature, so that the danger of disintegration of the light-sensitive compound no longer exists. Blurring due to light radiation from the vapor source is also no longer possible because the continuous movement'of the carrier ensures that the lightsensitive compound will be created or chemically formed only after the particular portion of the carrier has progressed out of the radiation range of the vapor source.

Quite understandably, the vapors need not be formed from materials contained in crucibles as described above.

' It is equally possible to obtain such vapors directly from the solid phase of the material involved by applying the latter to an electrically conductive body, such as a wire (not shown), which is then heated to the vaporization temperature of the material by electric current. Alternatively, said body itself may be vaporized together with the coating of the light-sensitive material, as by capacitor discharge.

In lieu of the crucibles of Fig. 3, for example, two separate wires (not shown) may be employed. Each wire is coated or otherwise provided with one component of the light-sensitive material, placed into an isolated evacuated chamber, and there heated to vaporize the particular component material associated therewith. The base strip is then guided past both chambers. Of course, this arrangement is employed only when it is desired to delay formation of the light-sensitive compound until the individual vapors condense on the surface of the film base.

Since the emissivity of the vapor source at low temperature depends substantially on the degree of vacuum in the vaporizing space or chamber, it is preferable to keep such vaporizing chamber as small as possible. In such a case, it becomes necessary to dispose both the supply spool or feed roll and the empty spool or take-up roll exteriorly of the vaporizing chamber and to provide a pair of vacuum locks in said chamber to provide entry or ingress and exit or egress means for the base or carrier.

To facilitate this, as may be seen from Fig. 4, rolls or spools 17 and 18 are disposed in a housing or chamber 20 surrounding vaporizing chamber 21, said housing being also and separately evacuated. To provide access for carrier 11 from housing 20' to chamber 21 and from the latter back into housing 20, chamber 21 is provided with a pair of vacuum locks 22. Only guide or idler rollers 19 need therefore be mounted in vaporizing chamber 21. Inasmuch as the vaporizing chamber can thus be made much smaller than it would have to be if the spools were also to be mounted therein, a much better degree of vacuum is obtainable in the vaporizing chamber with an attendant increase of vapor emission.

It may occur that certain special carrier materials require some preliminary treatment of the surface thereof to facilitate condensation of the vapors of the light-sensitive substance. Such treatment may consist of a seeding or nucleation of said surface, i.e., of a vaporization of a quantity of silver and condensation of an extremely thin, initial layer of said silver on the carrier surface. The silver particles of this layer serve as nuclei for the condensed light-sensitive substance (in substantially the same manner as a single crystal may serve as a nucleus for build-up of a composite crystal structure) and make the carrier or base more receptive to said sensitive substances.

As may be seen from Fig. 5, such seeding or nucleation is effected by an arrangement substantially like that of Fig. 2. However, adjacent the path of movement of carrier 11 in advance of that portion of such path lying adjacent opening 16 of crucible 13 there is disposed a small, electrically heated crucible 23 in which the silver, to be used for forming the aforesaid initial layer on the surface of carrier 11, is contained. It will be readily apparent, of course, that such prellm' inary treatment may be accomplished before the carrier is moved past the main vapor source, i.e., crucible 13, or as part of a single operation with the formation of the light-sensitive layer.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it isgintended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

l. A process of producing a photographic photosensitive layer on a carrier base; comprising the steps of vaporizing by heating under a vacuum silver and bromine to form vapors thereof, directing onto said base said v apors for chemical inter-reaction, while unidirectionally and substantially continuously moving said base within said vacuum at predetermined speed, and bringing to condensation said vapors to thereby form silver bromide on said base.

2. A process according to claim 1, including the step of controlling said predetermined speed of said base to a rate sufiicient to prevent any light or heat created during said heating of said components from affecting said photosensitive compound deposited on said base.

3. A process of producing a photographic photosensitive layer on a carrier base; comprising the steps of vaporizing by heating under a vacuum chemical components of a photosensitive silver halide compound to form vapors of said components, directing onto said base said vapors of said components 'for chemical inter-reaction, while unidirectionally and substantially continuously moving said base within said vacuum at predetermined speed, and bringing to condensation said vapors to thereby form a photosensitive chemical compound on said base.

4. A process of producing a photographic photosensitive'layer on a carrier base; comprising the steps of vaporizing by heating under one vacuum chemical components of a photosensitive silver halide compound to form vapors of said components, directing onto saidbase said vapors of said components for chemical inter-reaction,

while unidirectionally and substantially continuously mov-' ing said base through said one vacuum from and back into a second vacuum at predetermined speed, and bringing to condensation said vapors to thereby form a photosensitive chemical compound on said base.

5. A process of producing photographic films having a light-sensitive layer on a base, comprising the steps of vaporizing individual separate chemical components of a light-sensitive substance from sources of vapors of said components and under'vacuumn, and unidirectionally and substantially continuously moving said base past and in the immediate vicinity of a discharge opening of said sources of vapors of said components of said substance while retaining said base in an unheated condition, whereby said vapors are condensed on said base in combined chemical formation directly upon passing through said discharge opening and to an extent depending on the rate of movement of said base past said sources, said vapors being formed from a liquid phase of said components of said substance, said components comprising silver and bromine.

6. A process of producing photographic films having a light-sensitive layer on a base, comprising the steps of vaporizing individual separate chemical components of a light-sensitive substance from sources of vapors of said components and under vacuum, and unidirectionally and substantially continuously moving said base past and in the immediate vicinity of a discharge opening of said sources of vapors of said components of said substance while retaining said base in an unheated condition, whereby said vapors are condensed on said base incombined chemical formation directly upon passing through said discharge opening and to an extent depending on the rate of movement of said base past said sources, said vapors being formed from a solid phase of said components of said substance, said components comprising silver and bromine.

7. A process of depositing a layer of a photosensitive silver halide compound on a carrier therefor, comprising the steps of placing said carrier under vacuum, forming separate vapors of component substances of said compound from respective sources of said substances under vacuum, moving said carrier past and in the immediate vicinity of respective discharge openings of said sources at a predetermined speed, and directing and conditioning said vapors immediately after the same pass through said discharge openings to combine chemically and form said compound and thereafter to condense on said carrier as the latter moves past said sources.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS OF PRODUCING A PHOTOGRAPHIC PHOTOSENSITIVE LAYER ON A CARRIER BASE, COMPRISING THE STEPS OF VAPORIZING BY HEATING UNDER A VACUUM SILVER AND BROMINE TO FORM VAPORS THEREOF, DIRECTING ONTO SAID BASE SAID VAPORS FOR CHEMICAL INTER-REACTION, WHILE UNDIRECTIONALLY AND SUBSTANTIALLY CONTINUOUSLY MOVING SAID BASE WITHIN SAID VACUUM AT PREDETERMINED SPEED, AND BRINGING TO CONDENSATION SAID VAPORS TO THEREBY FORM SILVER BROMIDE ON SAID BASE. 